It is conventional to supply current to an electromagnet from thermally responsive means including a thermocouple near a standing pilot to hold a safety valve open. For example, such as arrangement is disclosed in U.S. Pat. No. 3,303,866. Failure of the pilot then causes the safety valve to close, shutting off all combustible gas to the system. Unfortunately, many manual valves may be shut off manually and turned on manually a short time thereafter. This permits the pilot to go out and a dangerously large amount of unburned but combustible gas to collect within the combustion chamber.
One solution to this problem is disclosed in the above-mentioned patent.